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Adding placeholder Span debugger proxy #14749

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Nov 8, 2017
Merged

Adding placeholder Span debugger proxy #14749

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38dccd3
Adding placeholder Span debugger proxy.
ahsonkhan Oct 30, 2017
ffcdc6e
Remove unnecessary unsafe keyword.
ahsonkhan Nov 1, 2017
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1 change: 1 addition & 0 deletions src/mscorlib/shared/System.Private.CoreLib.Shared.projitems
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Expand Up @@ -438,6 +438,7 @@
<Compile Include="$(MSBuildThisFileDirectory)System\SerializableAttribute.cs" />
<Compile Include="$(MSBuildThisFileDirectory)System\Single.cs" />
<Compile Include="$(MSBuildThisFileDirectory)System\Span.cs" />
<Compile Include="$(MSBuildThisFileDirectory)System\SpanDebugView.cs" />
<Compile Include="$(MSBuildThisFileDirectory)System\Span.NonGeneric.cs" />
<Compile Include="$(MSBuildThisFileDirectory)System\String.Searching.cs" />
<Compile Include="$(MSBuildThisFileDirectory)System\StringSpanHelpers.cs" />
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1 change: 1 addition & 0 deletions src/mscorlib/shared/System/ReadOnlySpan.cs
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Expand Up @@ -15,6 +15,7 @@ namespace System
/// ReadOnlySpan represents a contiguous region of arbitrary memory. Unlike arrays, it can point to either managed
/// or native memory, or to memory allocated on the stack. It is type- and memory-safe.
/// </summary>
[DebuggerTypeProxy(typeof(SpanDebugView<>))]
[DebuggerDisplay("{DebuggerDisplay,nq}")]
[NonVersionable]
public readonly ref struct ReadOnlySpan<T>
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1 change: 1 addition & 0 deletions src/mscorlib/shared/System/Span.cs
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Expand Up @@ -21,6 +21,7 @@ namespace System
/// Span represents a contiguous region of arbitrary memory. Unlike arrays, it can point to either managed
/// or native memory, or to memory allocated on the stack. It is type- and memory-safe.
/// </summary>
[DebuggerTypeProxy(typeof(SpanDebugView<>))]
[DebuggerDisplay("{DebuggerDisplay,nq}")]
[NonVersionable]
public readonly ref struct Span<T>
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28 changes: 28 additions & 0 deletions src/mscorlib/shared/System/SpanDebugView.cs
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@@ -0,0 +1,28 @@
// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

using System.Diagnostics;
using System.Reflection;
using System.Runtime.CompilerServices;

namespace System
{
internal sealed class SpanDebugView<T>
{
private readonly T[] _array;

public SpanDebugView(Span<T> span)
{
_array = span.ToArray();
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I am not sure if making copy will work. You should talk to the debugger people or try on some other type wrapping an array. The reason is that I think the debugger instantiates just one proxy and then calls the properties on it multiple times (when it needs to refresh the view).

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@ahsonkhan ahsonkhan Nov 8, 2017 •
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I don't understand. If the instantiation only happens once and only the items property gets called, then wouldn't this issue cause problems while debugging slow span too (see SpanDebugView)?

Can you provide a code sample that would cause issues?

byte[] array = new byte[5] { 1, 2, 3, 4, 5 };

string[] strArray = new string[6] { "12", "ab", "agfs", "AGadg", "ag", "" };

var span = new Span<byte>(array, 1, 3);
Console.WriteLine(span.Length);

span = span.Slice(2);

var rospan = new ReadOnlySpan<byte>(array, 1, 3);
Console.WriteLine(rospan.Length);

var span2 = new Span<string>(strArray, 1, 3);
Console.WriteLine(span2.Length);
}

image

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}

public SpanDebugView(ReadOnlySpan<T> span)
{
_array = span.ToArray();
}

[DebuggerBrowsable(DebuggerBrowsableState.RootHidden)]
public T[] Items => _array;
}
}